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Public Health

Vetted resources and information on current public health events.

Overview of Bird Flu Outbreak in the U.S.

H5N1 Bird Flu U.S. Current Situation Summary

Highly pathogenic avian influenza (HPAI) A(H5) viruses have been detected in U.S. wild aquatic birds, commercial poultry and backyard or hobbyist flocks beginning in January 2022. These are the first detections of HPAI A(H5) viruses in the U.S. since 2016. Preliminary genetic sequencing and RT-PCR testing on some virus specimens shows these viruses are HPAI A(H5N1) viruses from clade 2.3.4.4.

NOTE: On March 29, 2024 the CDC announced new interim recommendations for prevention, monitoring, and public health investigations of highly pathogenic avian influenza A(H5N1) virus in animals. Updates to this page are forthcoming.


Overview of H5N1 Detections in the United States
Last Updated: April 10, 2024
 
Wild Birds:  Widespread Humans: 2 cases in the U.S.
Poultry Flocks: Sporadic outbreaks Person-to-person spread: None
Mammals:  Sporadic infections Current public health risk: Low

News and Updates on Bird Flu Outbreak in the U.S.

Updates on Highly Pathogenic H5N1 in U.S. Dairy Cows
  • April 11 -- Highly Pathogenic Avian Influenza has been found in a herd of dairy cows in North Carolina, according to state agriculture officials. Testing by the National Veterinary Services Laboratory recently found the virus in the North Carolina herd. State officials did not say where in North Carolina the infected herd is. The North Carolina Department of Agriculture said it already suspended bringing cattle to North Carolina from states with known bird flu infections. 
Update on the Human Infection with HPAI Avian Influenza A(H5N1) in Texas
  • A person in Texas tested positive for highly pathogenic avian influenza (HPAI) A(H5N1) virus (“H5N1 bird flu”). This is only the second case of H5N1 bird flu in the United States; the first was in a poultry worker in Colorado in 2022.
  • This person in Texas worked with dairy cows presumably infected with H5N1 bird flu viruses.
  • This is the first time this virus has been found in cows and would be the first instance of cow-to-human spread of bird flu.
  • CDC has sequenced the influenza virus genome from the patient in Texas and compared this with other sequenced H5N1 viruses. The virus obtained from this person is nearly identical to what has been found in cows and birds in Texas.
  • There are no changes associated with resistance to antiviral medications and the virus is closely related to two existing candidate vaccine viruses.
  • There is no sign of person-to-person spread of this virus at this time.
  • This is an emerging and rapidly evolving situation that CDC is following closely. At this time, CDC believes that the overall risk to the general public posed by this virus remains low.

CDC Recommendations: Human HPAI Avian Influenza A(H5N1) Infections

Recommendations for the General Public

While CDC believes the current risk to the general public remains low, people with close or long unprotected exposures (not wearing respiratory or eye protection) to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other animals, are at greater risk of infection.

To reduce the risk of infection:
  • People should avoid unprotected exposures to sick or dead animals, including wild birds, poultry, other domesticated birds, and other wild or domesticated animals (including cows).
  • People should avoid unprotected exposures to animal poop, bedding (litter), raw milk, or materials that have been touched by, or close to, birds or other animals with suspected or confirmed H5N1 bird flu.
  • People should not prepare or consume uncooked or undercooked food or related uncooked food products, such as unpasteurized (raw) milk, or raw cheeses, from animals with suspected or confirmed H5N1 bird flu virus infection.
  • It is safe to drink commercial milk because products are pasteurized before entering the market. Pasteurization kills bacteria and viruses, like influenza viruses, in milk.
  • It is safe to eat properly handled and cooked poultry in the United States. Properly handling and cooking poultry and eggs to an internal temperature of 165˚F kills bacteria and viruses, including bird flu viruses.
  • Specific recommendations for farmers; poultry, backyard flock, and livestock owners; and worker protection are also available.
Recommendations for Clinicians

Clinicians should consider the possibility of HPAI A(H5N1) virus infection in people showing signs or symptoms of acute respiratory illness or conjunctivitis and who have relevant exposure history outlined in Highly Pathogenic Avian Influenza A(H5N1) Virus in Animals: Interim Recommendations for Prevention, Monitoring, and Public Health Investigations.

 
Examples of symptoms include but are not limited to:
  • Mild illness: (e.g., cough, sore throat, eye redness or eye discharge such as conjunctivitis, fever or feeling feverish, rhinorrhea, fatigue, myalgia, arthralgia, and headache)
  • Moderate to severe illness: (e.g., shortness of breath or difficulty breathing, altered mental status, and seizures)
  • Complications: (e.g., pneumonia, respiratory failure, acute respiratory distress syndrome, multi-organ failure (respiratory and kidney failure), sepsis, and meningoencephalitis)
 
If signs and symptoms compatible with avian influenza A(H5N1) virus infection are present:
  1. Isolate patient and follow infection control recommendations, including using PPE.
  2. Initiate empiric antiviral treatment as soon as possible. Do not delay treatment while awaiting laboratory results.
  3. Notify state and local health department to arrange testing for influenza A(H5N1) virus.
  4. Collect respiratory specimens from the patient to test for influenza A(H5N1) virus at the state health department. If the exposed person has conjunctivitis, with or without respiratory symptoms, both a conjunctival swab and a nasopharyngeal swab should be collected for testing.
  5. Encourage patients to isolate at home away from their household members and not go to work or school until it is determined they do not have avian influenza A(H5N1) virus infection.

Starting empiric antiviral treatment with oral or enterically administered oseltamivir (twice daily for five days) is recommended regardless of time since onset of symptoms. Antiviral treatment should not be delayed while waiting for laboratory test results.

 
For more information:

H5N1 Detections in the U.S.

2022-2024 U.S. Detections of Highly Pathogenic Avian Influenza

The United States has the strongest avian influenza surveillance program in the world. Through our ongoing wild bird surveillance program, APHIS collects and tests large numbers of samples from wild birds in the North American flyways.

It is not uncommon to detect avian influenza in wild birds, as avian influenza viruses circulate freely in those populations without the birds appearing sick. In addition to monitoring for avian influenza in wild bird populations, APHIS monitors for the virus in commercial and backyard birds. 

With the recent detections of the Eurasian H5 strain of highly pathogenic avian influenza (HPAI) in wild birds and domestic poultry in the United States, bird owners should review their biosecurity practices and stay vigilant to protect poultry and pet birds from this disease. APHIS is working closely with State partners on surveillance, reporting, and control efforts.

Commercial and Backyard Poultry Flocks

APHIS confirmed highly pathogenic avian influenza (HPAI) in a commercial flock in the United States on February 8, 2022. Since then, we have worked swiftly to identify and respond to detections and mitigate the virus’ impact on U.S. poultry production and trade. Detections are higher in the fall and spring, because we continue to see wild birds spreading virus as they migrate to their seasonal homes. APHIS continues to work closely with State animal health officials on surveillance efforts to look for the virus in commercial, backyard, and wild birds.

Current Confirmed HPAI Detections in Commercial and Backyard Flocks

Wild Birds

Wild birds can be infected with highly pathogenic avian influenza (HPAI) and show no signs of illness. They can carry the disease to new areas when migrating, potentially exposing domestic poultry to the virus.

APHIS’ wild bird surveillance program provides an early warning system for the introduction and distribution of avian influenza viruses of concern in the United States, allowing APHIS and the poultry industry to take timely and rapid action to reduce the risk of spread to our poultry industry and other populations of concern.

Confirmed Detections in Wild Birds

Wild Mammals

There are many species that are potentially susceptible to highly pathogenic avian influenza (HPAI). In addition to birds and poultry, H5N1 viruses have been detected in some mammals (see list below). Infection may cause illness, including severe disease and death in some cases.

Confirmed Detections in Wild Mammals

Livestock

The U.S. Department of Agriculture, Food and Drug Administration, Centers for Disease Control and Prevention, and State veterinary and public health officials are investigating an illness among primarily older dairy cows.

Confirmed Detections in Domestic Livestock

Bird Flu Resources